This invention relates to magnetic disk drives and particularly to an actuator for moving the magnetic heads into position for reading from or writing on a magnetic disk.
Magnetic disk units are extensively used in computer systems. Large magnetic disk units generally have a magnetic read/write assembly which is moved radially from track to track across the magnetic disk. Recently, many small magnetic disk drives have employed an actuator which moves the heads in an arc across the magnetic disks, much in the manner of a phonograph arm moving across a record. An example of this type of drive is IBM System 32 and comparable magnetic disk drives made by other companies. These disk drives usually make use of a magnetic head which is referred to as "IBM/Winchester".
The actuator for these magnetic disk units includes a rotating coil which is coupled to the magnetic recording head assembly to position it with respect to the magnetic disk when the coil is energized. Permanent magnets are positioned on two sides (top and bottom) of the coil to cooperate with a pole piece in an assembly which produces the desired arcuate position when the coil is energized.
These rotary actuators use only two sides of their coil to produce torque. The side of the coil with the greatest lever arm is outside of the torque-producing magnetic air gap. For this reason, the prior art actuators do not maximize the torque available from a coil having a given number of windings.
It is an object of the present invention to provide an actuator having improved torque capability for a magnetic disk drive.
It is a further object of the present invention to provide an actuator which is easy to fabricate and cost-effective.